The nut elements of a musical instrument are designed to support a series of strings at the neck end of the instrument. A series of bridge saddles form part of an instrument bridge on the body of the instrument. The saddles are located at a bridge end which is opposite to the neck end. The saddles also support and allow for tuning adjustment of the strings.
Traditionally, conventional nut elements have consisted of a small rectangular bar fixedly positioned a fixed distance from the instrument bridge and extending above the fingerboard. The strings rest in tension in the nut to give string spacing above the fingerboard. The bar contains a series of grooves or slots in which strings of varying diameters are retained within the slots. To facilitate and maintain accurate tuning of the instrument, the strings must slide easily within the grooves of the nut and saddle. This also allows each string to slide forward and backward freely within its nut and saddle when the instrument utilizes a pivoting tremolo device at the bridge end of the instrument. The drawback of a conventional nut and conventional saddle is that often the strings will bind or constrict within the grooves of the nut, resisting needed movement to maintain tuning accuracy or when performing with a tremolo mechanism. Particularly, when the strings are constrained within the nut, it is difficult to properly tune and maintain consistent tuning of the instrument.
Alternative nut or saddle materials such as plastics, plastic composites including Teflon plastic and/or graphite have been employed, but these materials suffer significant frictional fatigue from repeated frictional string movement and must be replaced at regular intervals. It is further apparent that in the process of this frictional wear it becomes difficult to maintain the tuning accuracy of the instrument over time.
A nut for a string instrument is shown in U.S. Pat. No. 4,709,612 (Wilkinson) in which a series of roller elements are journalled within an elongated bore hole of a nut housing. The roller elements are confined to minimal increments of free rotational travel. Each of the roller elements is comprised of a series of cylindrical slugs which vary in diameter and come to rest at the bottom of the elongated axial bore hole in the nut housing. When the roller element is set into motion by a moving string, the roller element moves eccentrically within the bore hole effectively "rocking" within the confines of the bore walls. The roller attempts to climb the walls of the bore in the process of rolling forward or backward in conjunction with the motion of the string. When the roller element reaches the point of the upper most acclivity of the bore hole, the roller is forced against the wall of the bore hole and is inhibited from further free rotational movement, i.e., it jams. Since the roller may no longer rotate freely at this point, the string then frictionally drags over the roller element for the remainder of its forward motion. It is also seen in Wilkinson that as the diameter of the roller elements is increased in relation to the bore hole fixed diameter, that the length of free rotation of the larger roller elements within the bore hole decreases significantly. Further, it is noted that any minimum lateral motion of the string across a roller element may bring the string in contact with its respective groove or slot, which causes the string to vibrate against the slot wall creating unwanted buzzing or rattling in normal musical use. Additionally, the end-to-end mounted rollers can become canted changing the limits of travel and cause excessive frictional contact.
U.S. Pat. No. 2,191,776 (Schreiber) employs a series of grooved rollers which are journalled on a central shaft or axle. This configuration dictates that the rollers and their corresponding strings will lie in a horizontal plane across the surface of the nut. No provision is made to accommodate the height or spacing of the strings in relation to the convex curvature of a cambered fingerboard. Secondly, a roller may be easily offset toward a roller bearing wall through lateral string tension and may frictionally contact the wall of the housing, impeding roller movement. Thirdly, rollers will have a tendency to rattle against the bearing walls in the housing when a string is vibrating in a normal musical use.
U.S. Pat. No. 4,625,613 (Steinberger) shows an adjustable bridge which employs a series of saddles for supporting the strings. Each saddle includes cylindrically-shaped metal insert with a surrounding recess or groove for supporting a corresponding single string. U.S. Pat. No. 4,457,201 (Storey) shows saddle rollers of cylindrical shape have a central groove for supporting a string.
U.S. Pat. No. 3,599,524 (Jones) describes a series of nuts, each having a journalled roller, each nut being adjustably offset from one another longitudinally of the instrument fingerboard. U.S. Pat. No. 2,959,085 also shows a series of abutting rollers but with an eccentrically formed groove. U.K. Patent No. 3996 of Feb. 7, 1898 shows a grooved horizontal roller on a shaft forming string-receiving grooves.